This invention relates to the removal of liquid residues from the surfaces of a moving strip or sheet. More particularly, this invention relates to a device and a method for the removal of adhered liquid residues, such as coolant and/or lubricant residues, from the side marginal edges of a continuously moving metal strip or sheet, for example aluminum strip or sheet.
When liquid residues remain on the surfaces of metal strips and/or sheet products, these liquid residues can detrimentally affect the surface properties of the strip and/or sheet. For example, moisture remaining on the surfaces can stain and ultimately oxidize the surfaces, while lubricant residues, particularly water-based lubricant residues, can cause discoloration, oxidation and other undesired effects when for example the strip is coiled or the sheet product is stacked. Apart from the undesired appearance, liquid residues can affect the physical properties of the products. These detrimental effects were long recognized and there are several systems described in the prior art which were developed for the removal of residual liquids from moving surfaces. Most of these systems remove the residual liquids from the main surfaces of strips or sheet products, i.e. the top and bottom surfaces of these. Representative prior art liquid removal systems designed to remove residual liquids from moving strip and sheet surfaces are disclosed in the following U.S. Pat. Nos.: 3,192,752 (Dowd et al), 4,477,287 (Kush et al) and 4,691,549 (Adair).
While removal of the residual liquid from the top and bottom surfaces of moving strips and sheet products is very important, no lesser importance is attached to the removal of liquid residue or edge bead from the side marginal edges of moving strips and sheets. If the liquid edge bead remains on the side marginal edges of strip and sheet products, it is transferred to the top and bottom surfaces by deflector rolls and by capillary flow after stacking or coiling. The removal of the liquid edge bead is of equal importance to the removal of residual liquid from top and bottom surfaces in preserving the quality of the rolled products.
Some prior art systems were designed to attempt to remove the residual liquid from both the top and bottom surfaces of strips and sheets and also the liquid edge bead on the side marginal surface. The combination of these two functions is shown for example in U.S. Pat. No. 4,400,961 where air is used to blow liquid residues off from both the upper and lower surfaces of a moving strip and also from the longitudinal edges of the strip. The pattern of air jets directed to the surfaces of the strip and towards the edges is claimed to dislodge coolant remaining on these surfaces and aspirators energized to pull atomized coolant from the regions immediately above and below the strip for the elimination of residual coolant. Use of the device shown in the aforementioned patent, while suitable for the removal of coolant residues from the top and bottom surfaces of a moving strip, was found to lack the required efficiency for the elimination of the liquid edge bead from the side marginal edges of the strip. In addition, the space requirements for the above-described coolant removal device in the vicinity of the rolls of the rolling mill make the utilization of this device difficult. A special system, directed to the removal of liquid edge bead, is provided in U.S. Pat. No. 4,601,112 (Kush et al). This patent describes a method and a device wherein liquid edge bead is removed from rapidly moving strip and sheet edges by wiping of the edges with rollers and the application of vacuum in the vicinity of the rollers. While the device shown in the aforementioned patent allows effective removal of the liquid edge bead from side marginal edges of a continuously moving strip, it is a contacting, mechanical device that is easily damaged by strip breaks or other operational mishaps and it also requires substantial space for positioning the edge bead removal rollers and the vacuum means downstream from the rolling mill. This large space requirement may interfere with equipment positioned after the last roll of the rolling mill, for example, with the coiling apparatus generally employed for strips. Another reference, Japanese Publication 61-244530 to Sumitomo Chemical Industries KK (published on Oct. 30, 1986) discloses the removal of water from the surfaces and edges of a metal sheet-plastic film composites by blowing the water off with an air spray applied to the top and bottom surfaces of the composite through nozzles. The angles of the air nozzles are set at 15.degree.-60.degree. against the direction of movement of the composite as it exits the rolls and the air is blown towards the edge portions of the composite. Through the use of the angled air nozzles water is claimed to be removed from both the top and bottom surfaces of the composite and also from the edges. The arrangement of the air jets utilized in the aforementioned Japanese reference provides angular velocity factors incapable of creating turbulence at the edge region of the composite and consequently the device disclosed in the Japanese reference does not allow substantial and effective removal of all of the liquid edge bead. This is particularly true at high rolling speeds, which are generally utilized in the rolling of metal strips and sheet, for example at speeds from about 500 to about 6000 feet/minute (153-1830 meters/minute) even the removal of water from the top and bottom surfaces will be less than satisfactory.
It is the purpose of this invention to provide an edge bead removal method and device which at the rates of speed generally utilized in the rolling of metal strips and sheet, particularly aluminum strip and sheet, substantially and effectively remove liquid edge bead adhering to the side marginal surfaces of the strips and sheet. This is accomplished by using, instead of the conventional air jets, vertical air curtains so that the velocity factor in the edge region of the moving strip or sheet is essentially parallel to the plane of the edge surface. The term "air", as used hereinafter, encompasses air, nitrogen and inert gases. The turbulence created in the edge region allows substantial and effective removal of the liquid edge bead both at conventional and at high rolling speeds.